What led scientists to develop the three domain system?

Scientists developed the three-domain system in response to molecular evidence, particularly the analysis of ribosomal RNA (rRNA) sequences. In 1977, Carl Woese and his colleagues discovered significant differences in the 16S rRNA sequences between certain prokaryotes, leading to the identification of Archaea as a distinct group separate from Bacteria. This molecular data prompted the reclassification of life into three domains: Archaea, Bacteria, and Eukarya.